Communication control apparatus, communication control method, and communication system

ABSTRACT

There is provided a communication control apparatus including a parameter acquisition unit that acquires parameters to calculate coverage of secondary systems from a secondary usage node operating the secondary systems on a frequency channel allocated to a primary system, a calculation unit that calculates the coverage of the secondary systems using the parameters acquired by the parameter acquisition unit, and an interference control unit that notifies a detection node that detects neighboring secondary systems of the secondary systems, of coverage information representing the coverage of the secondary systems calculated by the calculation unit.

TECHNICAL FIELD

The present disclosure relates to a communication control apparatus, acommunication control method, a program, and a communication system.

BACKGROUND ART

As one of measures to mitigate exhaustion of frequency resources in thefuture, the discussion about secondary usage of a frequency is underway. The secondary usage of a frequency is to use a part or all of afrequency channel preferentially assigned to some system secondarily byanother system. In general, the system to which a frequency channel ispreferentially assigned is called a primary system and the system thatsecondarily uses the frequency channel is called a secondary system.

A TV white space is an example of the frequency channel discussed forsecondary usage. The TV white space refers to, among frequency channelsassigned to a TV broadcasting system as a primary system, a channel thatis not used by the TV broadcasting system depending on the region. Byreleasing the TV white space for secondary usage, efficient utilizationof frequency resources can be realized. As specifications of thewireless access method of the physical layer (PHY) and the MAC layer toenable secondary usage of the TV white space, for example, a pluralityof standard specifications like IEEE802.22, IEEE802.11af, and ECMA(European Computer Manufacturer Association)-392 (CogNea) is known.

The IEEE802.19 is currently working to allow smooth coexistence of aplurality of secondary systems using different wireless access methods.For example, Non-Patent Literature 1 below divides various functionsneeded for coexistence of secondary systems into three functionalentities of CM (Coexistence Manager), CE (Coexistence Enabler), and CDIS(Coexistence Discovery and Information Server). CM is a functionalentity that mainly makes a decision for coexistence. CE is a functionalentity to be an interface that mediates instruction transmission orinformation exchange between CM and a secondary usage node. CDIS is afunctional entity to be a server that manages information of a pluralityof secondary systems in a unified manner. CDIS also has a neighbordiscovery function which detects neighboring secondary systems that mayinterfere with each other.

CITATION LIST Non-Patent Literature

Non-Patent Literature 1: “Coexistence System Description”, [online],[Searched on Mar. 17, 2011], the Internet<URL:https://mentor.ieee.org/802.19/dcn/11/19-11-0011-01-0001-coexistence-system-description.pdf>

SUMMARY OF INVENTION Technical Problem

However, to detect a neighboring secondary system (hereinafter, called aneighboring system) that may interfere with each other, the collectionof various parameters to calculate coverage of each secondary system isdemanded. Thus, when one functional entity attempts to perform neighbordetection in a unified manner, the load of calculation processing of theone functional entity and the load of traffic accompanying the parametercollection increase if the number of secondary systems is large. If aplurality of functional entities can perform neighbor detection incooperation, by contrast, it is expected that the above concentration ofload can be avoided so that a plurality of secondary systems can beoperated smoothly.

Solution to Problem

According to an embodiment of the present disclosure, there is provideda communication control apparatus including a parameter acquisition unitthat acquires parameters to calculate coverage of secondary systems froma secondary usage node operating the secondary systems on a frequencychannel allocated to a primary system, a calculation unit thatcalculates the coverage of the secondary systems using the parametersacquired by the parameter acquisition unit, and an interference controlunit that notifies a detection node that detects neighboring secondarysystems of the secondary systems, of coverage information representingthe coverage of the secondary systems calculated by the calculationunit.

Further, according to an embodiment of the present disclosure, there isprovided a communication control method of a control node that controlscommunication by a secondary usage node operating secondary systems on afrequency channel allocated to a primary system, the method includingacquiring parameters to calculate coverage of the secondary systems fromthe secondary usage node, calculating the coverage of the secondarysystems using the acquired parameters, and notifying a detection nodethat detects neighboring secondary systems of the secondary systems, ofcoverage information representing the calculated coverage of thesecondary systems.

Further, according to an embodiment of the present disclosure, there isprovided a communication control system including a secondary usage nodethat operates secondary systems on a frequency channel allocated to aprimary system, a control node that controls communication by thesecondary usage node, and a detection node that detects neighboringsecondary systems of the secondary systems. The control node includes aparameter acquisition unit that acquires parameters to calculatecoverage of the secondary systems from the secondary usage node, acalculation unit that calculates the coverage of the secondary systemsby using the parameters acquired by the parameter acquisition unit, andan interference control unit that notifies the detection node ofcoverage information representing the coverage of the secondary systemscalculated by the calculation unit.

Advantageous Effects of Invention

According to the present disclosure, as described above, theconcentration of load accompanying neighbor detection for coexistence ofsecondary systems can be avoided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory view illustrating an overview of acommunication system according to an embodiment.

FIG. 2 is an explanatory view showing correlations among threefunctional entities to support coexistence.

FIG. 3 is an explanatory view showing an example of arrangement of thefunctional entities.

FIG. 4 is a flow chart showing an example of the flow of communicationcontrol processing for general neighbor detection.

FIG. 5 is an explanatory view showing a first example of the physicalrelationship of secondary systems.

FIG. 6 is an explanatory view showing a second example of the physicalrelationship of secondary systems.

FIG. 7 is a block diagram showing an example of a configurationaccording to an embodiment of a communication control apparatuscorresponding to CM.

FIG. 8 is a block diagram showing an example of the configurationaccording to an embodiment of the communication control apparatuscorresponding to CDIS.

FIG. 9 is an explanatory view illustrating a first example of coverageinformation generated by CM in an embodiment.

FIG. 10 is an explanatory view illustrating detection of neighboringsystems based on the coverage information illustrated in FIG. 9.

FIG. 11 is an explanatory view illustrating a second example of thecoverage information generated by CM in an embodiment.

FIG. 12 is a first explanatory view illustrating an example of aneighboring system list generated by CDIS in an embodiment.

FIG. 13 is a second explanatory view illustrating an example of theneighboring system list generated by CDIS in an embodiment.

FIG. 14 is a flow chart showing an example of the flow of communicationcontrol processing for neighbor detection according to an embodiment.

FIG. 15 is a flow chart showing an example of the flow of communicationcontrol processing for neighbor detection according to a firstmodification.

FIG. 16 is a flow chart showing an example of the flow of communicationcontrol processing for neighbor detection according to a secondmodification.

DESCRIPTION OF EMBODIMENT

Hereinafter, preferred embodiments of the present disclosure will bedescribed in detail with reference to the appended drawings. Note that,in this specification and the drawings, elements that have substantiallythe same function and structure are denoted with the same referencesigns, and repeated explanation is omitted.

The description will be provided in the following order:

1. System Overview

-   -   1-1. Overall System Configuration    -   1-2. Description of Functional Entities    -   1-3. Arrangement Example of Functional Entities    -   1-4. Flow of Processing for General Neighbor Detection    -   1-5. Explanation of Problem in an Embodiment

2. Configuration Example of Apparatus According to an Embodiment

-   -   2-1. CM    -   2-2. CDIS    -   2-3. Data Example

3. Flow of Processing According to an Embodiment 4. Modifications

-   -   4-1. First Modification    -   4-2. Second Modification

5. Summary

-   -   <1. System Overview>    -   [1-1. Overall System Configuration]

FIG. 1 is an explanatory view illustrating an overview of acommunication system according to an embodiment.

Referring to FIG. 1, a primary transmitting station 10 constituting aprimary system and a plurality of primary receiving stations 12 areshown. The primary transmitting station 10 provides a primary systemservice to the primary receiving stations 12 positioned inside a servicearea 14. The primary transmitting station 10 may be, for example, abroadcasting station of TV broadcasting or a wireless base station or arelay station of a cellular communication method. When the primarytransmitting station 10 is a broadcasting station of TV broadcasting,the primary receiving station 12 is a receiver having a receivingantenna for TV broadcasting and a tuner. When the primary transmittingstation 10 is a wireless base station of a cellular communicationmethod, the primary receiving station 12 is a wireless terminaloperating according to the cellular communication method. In thedescription that follows, the primary transmitting station 10 and theprimary receiving station 12 may generically be called primary usagenodes.

The primary transmitting station 10 is connected to a data server 20positioned in a packet-based network 16. The packet-based network 16 maybe the Internet or a backbone network of a primary system. The dataserver 20 is a server apparatus having a database storing data onsecondary usage of secondary channels. At least one of communicationcontrol apparatuses 30 is connected to the data server 20. Thecommunication control apparatus 30 is an apparatus introduced to controlcoexistence among a plurality of secondary systems using frequencychannels assigned to a primary system.

In FIG. 1, a plurality of secondary usage nodes 40, 42 is further shown.The secondary usage node 40 is an apparatus that provides a secondarysystem service (hereinafter, called a secondary communication service)to the secondary usage node 42 positioned inside a service area 44 byusing a frequency channel assigned to a primary system. When the primarysystem is a TV broadcasting system, the secondary usage node 40 is alsocalled a master TVBD (TV Band Device). The secondary usage node 40 istypically has a geo-location function and a function to access thecommunication control apparatus 30. The secondary usage node 40 maydirectly be accessible to the data server 20. The secondary usage node42 is an apparatus positioned inside each of the service areas 44 to usethe secondary communication service provided by the secondary usage node40. When the primary system is a TV broadcasting system, the secondaryusage node 42 is also called a slave TVBD. In principle, the secondaryusage node 42 transmits a radio signal after obtaining permission fromthe nearby secondary usage node 40.

The secondary usage node 40 registers information about a secondarysystem with the data server 20 before starting the operation of thesecondary system. Then, the secondary usage node 40 operates thesecondary system based on control information provided from the dataserver 20. However, when a plurality of secondary systems is operated inparallel like the situation shown in FIG. 1, the risk of fatallyaffecting the primary system may be incurred due to collisions ofsignals between secondary systems or overlapping interference caused bysignals transmitted from each secondary system. Particularly, when thewireless access methods used by secondary systems are different, it isdifficult to operate the system while maintaining cooperation amongsecondary systems, further raising the above risk. Thus, the IEEE802.19is working on a mechanism to smoothly support coexistence of a pluralityof secondary systems (see Non-Patent Literature 1 described above). InIEEE802.19, various functions to support coexistence of secondarysystems are divided into three groups of functional entities of CM, CE,and CDIS (see FIG. 2).

-   -   [1-2. Description of Functional Entities]    -   (1) CM (Coexistence Manager)

CM is a functional entity that makes a decision for coexistence. CMacquires information about a primary system, information about availablechannels, and information about secondary systems. Sources from whichinformation is acquired by CM include CDIS, other CM, and secondaryusage nodes (accessed via CE). Based on the above information, CMdecides which frequency channel to be used by a secondary usage nodeunder the control thereof to operate the secondary system. CM mayfurther decide additional control parameters such as the maximumtransmission power, recommended wireless access method, and period ofupdating position data for each secondary usage node. Then, according todecided parameters, CM allows each secondary usage node to operate asecondary system or to reconfigure a secondary system.

-   -   (2) CE (Coexistence Enabler)

CE is a functional entity to be an interface that mediates instructiontransmission or information exchange between CM and a secondary usagenode. For example, CE converts information held by a secondary usagenode into a format that can be used by CM and transmits the convertedinformation to the CM. CE also converts an instruction about coexistenceof secondary systems from CM into a format that can be executed by asecondary usage node and transmits the converted information to thesecondary usage node.

-   -   (3) CDIS (Coexistence Discovery and Information Server)

CDIS is a functional entity to be a server that manages information of aplurality of secondary systems. For example, CDIS collects informationabout secondary systems from each secondary usage node via CE and CM.CDIS also collects information about the primary system and informationabout available channels from the data server 20. Then, CDIS storescollected information in a database. The information stored by CDIS isused when a decision about coexistence is made by CM. CDIS may selectmaster CM (CM that supervises a plurality of CM and makes a decisionintensively) among a plurality of CM. CDIS also has a neighbor discoveryfunction which detects neighboring secondary systems that may interferewith each other.

At least one of the above three functional entities is implemented ineach of the communication control apparatuses 30 shown in FIG. 1.Incidentally, a part of the functional entities may be implemented onthe individual secondary usage nodes 40. In addition, a part of thefunctional entities may also be implemented in the same apparatus as thedata server 20.

-   -   [1-3. Arrangement Example of Functional Entities]

The above three functional entities may be arranged in each apparatus asshown, for example, in FIG. 3. The arrangement of the functionalentities described here is only by way of example and other arrangementsmay also be used.

Referring to FIG. 3, CDIS is arranged in a communication controlapparatus 30 a and CM is arranged in each of two communication controlapparatuses 30 b. First CM (CM#A) is arranged in one of thecommunication control apparatuses 30 b to which secondary usage nodes 40a, 40 b belong. Second CM (CM#B) is arranged in the other communicationcontrol apparatus 30 b to which secondary usage nodes 40 c, 40 d belong.The secondary usage node 40 a operates a secondary system N1 togetherwith a secondary usage node 42 a. The secondary usage node 40 b operatesa secondary system N2 together with a secondary usage node 42 b. Thesecondary usage node 40 c operates a secondary system N3 together with asecondary usage node 42 c. The secondary usage node 40 d operates asecondary system N4 together with a secondary usage node 42 d. CE isarranged on each of the secondary usage nodes 40 a, 40 b, 40 c, 40 d.Thus, each of the secondary usage nodes 40 as master devices operatingeach secondary system has at least CE to interact with CM.

-   -   [1-4. Flow of Processing for General Neighbor Detection]

When functional entities are arranged as shown in the example of FIG. 3,processing for general neighbor detection may be performed in the flowshown in FIG. 4.

Referring to FIG. 4, each of the secondary usage nodes 40 a, 40 b firstcollects parameters to calculate coverage (that is, the communicationrange or the range of service area) of each secondary system (step S11).Similarly, each of the secondary usage nodes 40 c, 40 d collectsparameters to calculate coverage of each secondary system (step S12).Parameters collected here include at least one of the position of eachsecondary usage node, antenna height, maximum transmission power,antenna gain, and minimum reception sensitivity.

Next, each of the secondary usage nodes 40 a, 40 b transmits a parameterlist containing collected parameters to the communication controlapparatus (CM#A) 30 b (step S13). Similarly, each of the secondary usagenodes 40 b, 40 c transmits a parameter list containing collectedparameters to the communication control apparatus (CM#B) 30 b (stepS14). The communication control apparatus (CM#A) 30 b transfers theacquired parameter list to the communication control apparatus (CDIS) 30a (step S15). Similarly, the communication control apparatus (CM#B) 30 btransfers the acquired parameter list to the communication controlapparatus (CDIS) 30 a (step S16).

The communication control apparatus (CDIS) 30 a uses the acquiredparameter lists to calculate coverage of all secondary systems undercontrol (step S20). Next, the communication control apparatus (CDIS) 30a determines the possibility of interference for each combination ofsecondary systems to detect neighboring systems (step S30). Then, thecommunication control apparatus (CDIS) 30 a provides a neighboringsystem list describing combinations of detected neighboring systems tothe communication control apparatus (CM#A) 30 b and the communicationcontrol apparatus (CM#B) 30 b (steps S41, S42).

Next, if the neighboring system list indicates the presence of secondarysystems that may interfere with each other, the communication controlapparatus

(CM#A) 30 b and the communication control apparatus (CM#B) 30 bnegotiate to control interference (step S50). For example, at least oneof the utilized channel of neighboring systems, wireless access method,and maximum transmission power may be adjusted by the negotiations here.Then, one or both of the communication control apparatus (CM#A) 30 b andthe communication control apparatus (CM#B) 30 b instruct the secondaryusage nodes 40 to configure or reconfigure the system to reflect anegotiation result in the configuration of each secondary system (stepsS61, S62).

-   -   [1-5. Explanation of Problem in an Embodiment]

In the flow of processing for neighbor detection shown in FIG. 4, CDISin the coexistence system performs neighbor detection of all secondarysystems under control in a unified manner. To perform neighbordetection, it is necessary for CDIS to collect parameters to calculatecoverage of all secondary systems. However, with an increasing number ofsecondary systems, the load of traffic accompanying the parameterconnection by CDIS may adversely affect the network. In addition, theload of calculation processing for neighbor detection may exceed theprocessing capacity of CDIS.

Referring to FIG. 5, for example, coverage of the secondary system N1operated by the secondary usage node 40 a and that of the secondarysystem N2 operated by the secondary usage node 40 b overlap. Thus, thesecondary systems N1, N2 are mutually neighboring systems. Because thesecondary usage nodes 40 a, 40 b belong to the communication controlapparatus (CM#A) 30 b, the communication control apparatus (CM#A) 30 bcan grasp that the secondary systems N1, N2 are mutually neighboringsystems. Also, coverage of the secondary system N3 operated by thesecondary usage node 40 c and that of the secondary system N4 operatedby the secondary usage node 40 d overlap. Thus, the secondary systemsN3, N4 are mutually neighboring systems. Because the secondary usagenodes 40 c, 40 d belong to the communication control apparatus (CM#B) 30b, the communication control apparatus (CM#B) 30 b can grasp that thesecondary systems N3, N4 are mutually neighboring systems. Under suchcircumstances, it is assumed that, as shown in FIG. 6, a new secondaryusage node 40 e that operates a secondary system N5 further appears andthe secondary usage node 40 e belongs to the communication controlapparatus (CM#A) 30 b. Coverage of the secondary system N5 overlaps withthat of the secondary system N2 and that of the secondary system N3.However, the communication control apparatus (CM#A) 30 b does not knowthe presence of the secondary system N3 and coverage thereof and socannot recognize mutual interference between the secondary system N5 andthe secondary system N3. In addition, the communication controlapparatus (CM#B) 30 b does not know the appearance of the secondarysystem N5 and coverage thereof and so cannot recognize mutualinterference between the secondary system N3 and the secondary systemN5.

That is, in a coexistence system in which a plurality of secondarysystems participate, the presence of a node that determines thepossibility of interference between secondary systems extending over CMis indispensable. However, as described above, the load of calculationprocessing of CDIS in the existing mechanism and the load of trafficaccompanying the parameter collection could prevent a smooth operationof a plurality of secondary systems.

When a plurality of communication operators (including broadcastingoperators) operates systems, needs for each operator to avoid thedisclosure of detailed parameters of the system to other operators asmuch as possible may arise. However, it is difficult to meet such needsin a configuration in which one CDIS collects parameters of allsecondary systems.

Thus, in an embodiment described in the next and subsequent sections,the above problem of load is avoided and also smooth coexistence systemsoperated by a plurality of operators is enabled by offloading a part ofgeneral functions of CDIS to CM to reduce the amount of data transmittedfrom CM to CDIS.

-   -   <2. Configuration Example of Apparatus According to an        Embodiment>    -   [2-1.CM]

FIG. 7 is a block diagram showing an example of the configuration of thecommunication control apparatus 30 b according to the presentembodiment. The communication control apparatus 30 b is an apparatusequivalent to CM. From the viewpoint of simplicity of the description,the description of functions of CM other than the function related toneighbor detection is omitted here. Referring to FIG. 7, thecommunication control apparatus 30 b includes a first communication unit110, a second communication unit 120, a storage unit 130, and a controlunit 140.

The first communication unit 110 is a communication interface thatmediates communication between the communication control apparatus 30 band the secondary usage node 40. The first communication unit 110supports any wireless communication protocol or wire communicationprotocol to establish communication connection between the communicationcontrol apparatus 30 b and at least the one secondary usage node 40.

The second communication unit 120 is a communication interface thatmediates communication between the communication control apparatus 30 band the other communication control apparatus 30. The secondcommunication unit 120 typically supports a packet-based (wire orwireless) communication protocol to establish communication connectionbetween the communication control apparatus 30 b and the othercommunication control apparatus 30.

The storage unit 130 is configured by a semiconductor memory or astorage medium such as a hard disk and stores programs and data forprocessing by the communication control apparatus 30 b. Data stored inthe storage unit 130 may include, for example, a parameter listcollected by the secondary usage node 40, coverage information generatedby the control unit 140 described below, and a neighboring system listprovided by the communication control apparatus 30 a.

The control unit 140 corresponds to a processor such as a CPU (CentralProcessing Unit) or DSP (Digital Signal Processor). The control unit 140allows the function of CM according to the present embodiment to becarried out by executing programs stored in the storage unit 130 oranother storage medium. More specifically, the control unit 140 includesa parameter acquisition unit 142, a calculation unit 144, and aninterference control unit 146.

The parameter acquisition unit 142 acquires parameters to calculatecoverage of a secondary system from each of the secondary usage nodes 40operating the secondary system on a frequency channel allocated to theprimary system via the first communication unit 110. Coverage of asecondary system herein refers to the service area of each secondarysystem or the geographical range of an area in which communication canbe performed. The range of a guard area that may be provided on theouter circumference of the service area may also be included in coverage(or may not be included). Parameters to calculate coverage of asecondary system may include at least one parameter of the position ofeach secondary usage node, antenna height, maximum transmission power,antenna gain, and minimum reception sensitivity.

The calculation unit 144 calculates coverage of each secondary systemusing parameters acquired by the parameter acquisition unit 142.

For example, the calculation unit 144 may calculate coverage of eachsecondary system according to the technique using, as the firsttechnique, a propagation path curve described in “Method forpoint-to-area predictions for terrestrial services in the frequencyrange 30 mhz to 3000 mhz” (International TelecommunicationsCommission(ITU), RECOMMENDATION ITU-R P1546-3, 2007). According to thefirst technique, a statistical curve (propagation path curve) based onmeasured values to derive a communication distance (communicabledistance at a fixed location rate and a fixed hour rate) from theantenna height and electric field strength is stored in the storage unit130 in advance. Then, the calculation unit 144 converts the maximumtransmission power of the secondary usage node 40 into electric fieldstrength to acquire the communication distance corresponding to theantenna height of the secondary usage node 40 and the electric fieldstrength from the propagation path curve. The communication distancebecomes the radius of coverage of the secondary system operated by thesecondary usage node 40.

Instead, as the second technique, the calculation unit 144 may calculatecoverage of each secondary system according to the technique using anevaluation formula in the urban district model (see “DEJITARU WAIYARESUDENSOU GIJUTSU (Digital Wireless Transmission Technique)” (by SeiichiSampei, Pearson Education Japan, pp. 16-19)) of the Okumura/Hata curve.In this case, the calculation unit 144 calculates the maximum allowablepath loss from the maximum transmission power of the secondary usagenode 40 and the minimum reception sensitivity of the secondary usagenode 42. Then, the calculation unit 144 calculates the communicationdistance by substituting the calculated path loss and the antenna heightinto the evaluation formula. The communication distance becomes theradius of coverage of the secondary system operated by the secondaryusage node 40.

If no wireless signal of a secondary system is received in a specificposition as a result of sensing by the secondary usage node 42, thecalculation unit 144 may exclude the position from coverage of thesecondary system.

The interference control unit 146 notifies a detection node that detectsneighboring systems by determining the possibility of interferencebetween secondary systems of coverage information representing coverageof each secondary system under control calculated by the calculationunit 144. In the present embodiment, the detection node is thecommunication control apparatus 30 a having CDIS. The coverageinformation of which CDIS is notified from the interference control unit146 may be map information indicating whether each of a plurality ofgeographical blocks belongs to coverage of each secondary system.Instead, the coverage information may be information indicating thereference position (for example, the position of the secondary usagenode 40 as the master TVBD) and the radius of coverage of each secondarysystem. A concrete example of coverage information will be described indetail later. When coverage information is notified from theinterference control unit 146 of each of the communication controlapparatuses 30 b, the communication control apparatus 30 a determinesthe possibility of interference for each combination of secondarysystems to detect neighboring systems. Then, the communication controlapparatus 30 a provides a list of detected neighboring systems to eachof the communication control apparatuses 30 b.

If a secondary system under control and a secondary system controlled bythe other communication control apparatus 30 b are indicated to bemutually neighboring systems by the neighboring system list provided bythe communication control apparatus 30 a, the interference control unit146 negotiates with the other communication control apparatus 30 b tocontrol interference between the neighboring systems. For example, ifdifferent frequency channels can be used between the neighboringsystems, the interference control unit 146 may allow to change theutilized channel of one or both of the secondary systems. If bothneighboring systems can use wireless access methods supporting the meshprotocol, the interference control unit 146 may allow to form a meshnetwork by assigning a common frequency channel to the neighboringsystems. If one or both of the neighboring systems can be allowed toreduce coverage by lowering the maximum transmission power, theinterference control unit 146 may instruct the secondary systems tolower the maximum transmission power. Accordingly, interference betweenthe neighboring system can be controlled.

-   -   [2-2.CDIS]

FIG. 8 is a block diagram showing an example of the configuration of thecommunication control apparatus 30 a according to the presentembodiment. The communication control apparatus 30 a is an apparatusequivalent to CDIS. From the viewpoint of simplicity of the description,the description of functions of CDIS other than the function related toneighbor detection is omitted here. Referring to FIG. 8, thecommunication control apparatus 30 a includes a communication unit 150,a storage unit 160, and a control unit 170.

The communication unit 150 is a communication interface that mediatescommunication between the communication control apparatus 30 a and thedata server 20 or the other communication control apparatus 30. Thecommunication unit 150 typically supports a packet-based (wire orwireless) communication protocol to establish communication connectionbetween the communication control apparatus 30 a and another apparatus.

The storage unit 160 is configured by a semiconductor memory or astorage medium such as a hard disk and stores programs and data forprocessing by the communication control apparatus 30 a. Data stored inthe storage unit 160 includes, for example, coverage information of eachsecondary system notified from the communication control apparatus 30 band a neighboring system list generated by the control unit 170described below.

The control unit 170 corresponds to a processor such as a CPU or DSP.The control unit 170 allows the function of CDIS according to thepresent embodiment to be carried out by executing programs stored in thestorage unit 160 or another storage medium. More specifically, thecontrol unit 170 includes a data management unit 172 and a neighbordetection unit 174.

The data management unit 172 manages various kinds of information forcoexistence of a plurality of secondary systems. For example, the datamanagement unit 172 periodically acquires information about the primarysystem (for example, coverage of the primary system, the position of aprimary receiving station, and a list of channels available forsecondary usage) from the data server 20 and causes the storage unit 160to store the acquired information. In addition, the data management unit172 causes the storage unit 160 to store information (for example, theabove coverage information) about secondary systems notified from thecommunication control apparatus 30 b. Then, the data management unit 172provides information the storage unit 160 is caused to store to thecommunication control apparatus 30 b in response to a request from thecommunication control apparatus 30 b.

The neighbor detection unit 174 determines the possibility ofinterference between a plurality of secondary systems when coverageinformation of the secondary systems is notified from the communicationcontrol apparatus 30 b via the communication unit 150. For example, theneighbor detection unit 174 may determine that interference is possiblebetween secondary systems in which coverage of one system overlaps withthat of the other system. Even if there is no overlapping coverage, theneighbor detection unit 174 may determine that interference is possiblebetween secondary systems if the shortest distance between outercircumferences of coverage is below a predetermined threshold. Whensecondary systems that may interfere with each other are detected, theneighbor detection unit 174 generates a neighboring system list thatdescribes the secondary systems as neighboring systems. Then, theneighbor detection unit 174 provides the generated neighboring systemlist to the communication control apparatus 30 b. A concrete example ofthe neighboring system list will be described in detail later.

-   -   [2-3. Data Example]    -   (1) Coverage Information    -   (1-1) First Example

FIG. 9 is an explanatory view illustrating a first example of coverageinformation generated by the communication control apparatus 30 b in thepresent embodiment. A plurality of blocks formed by dividing ageographical region is shown on the upper left corner of FIG. 9. Thecalculation unit 144 of the communication control apparatus 30 bcalculates the range of a service area 44 present extending over one ormore blocks as coverage for each secondary system. Then, the calculationunit 144 generates coverage information in a bitmap form indicatingwhether each block belongs to the calculated coverage. Coverageinformation of a secondary system Ni in which a block not belonging tocoverage is set to 0, a block belonging to coverage is set to 1, and acenter block of coverage containing the reference position is set to 2is shown on the lower right corner of FIG. 9. However, coverageinformation is not limited the example in FIG. 9 and the shape of eachblock may be any shape other than the rectangle (for example, thetriangle or hexagon).

FIG. 10 is an explanatory view illustrating detection of neighboringsystems based on the coverage information illustrated in FIG. 9.Coverage information of two secondary systems Ni, Nj of which thecommunication control apparatus 30 a may be notified from thecommunication control apparatus 30 b is shown in the upper part of FIG.10. The neighbor detection unit 174 of the communication controlapparatus 30 a calculates a logical conjunction of values of two piecesof coverage information for each block of the coverage information. As aresult, as shown in the lower part of FIG. 10, a bitmap in which onlyblocks of overlapping coverage have values other than 0 is derived.Thus, if a bitmap contains a value other than 0, the two secondarysystems may be determined to have the possibility of interference witheach other. If the bitmap contains the value “2”, it is understood thata wireless signal from the secondary usage node 40 as the master deviceof one secondary system can directly reach the secondary usage node 40of the other secondary system.

Thus, when the first example of coverage information is adopted, theneighbor detection unit 174 of the communication control apparatus 30 acan easily determine the possibility of interference between secondarysystems by repeating the operation of a simple logical conjunction.

In the first example of coverage information, the value of each blockmay indicate a power level of a wireless signal of the secondary systemassumed in each block. Accordingly, though the amount of data ofcoverage information increases, it becomes possible to estimate not onlythe possibility of interference, but also intensity of interference indetail by the neighbor detection unit 174 of the communication controlapparatus 30 a.

-   -   (1-2) Second Example

FIG. 11 is an explanatory view illustrating a second example of coverageinformation generated by the communication control apparatus 30 b in thepresent embodiment. In the second example, coverage information isinformation indicating the reference position and radius of coverage ofeach secondary system in a list form.

Coverage information of which the communication control apparatus (CDIS)30 a is notified from the communication control apparatus (CM#A) 30 b isshown on the left side of FIG. 11. The coverage information contains thesecondary system ID, reference position (position of the secondary usagenode 40), and radius (for example, the radius of the service area aroundthe reference position) of the secondary systems N1, N2, N5 illustratedin FIG. 6. Further, in the present embodiment, a change sectionindicating whether coverage is changed is attached to coverageinformation for each secondary system. In the example of FIG. 11, thechange section (“New”) of the secondary system N5 indicates thatcoverage information of the secondary system N5 is newly added. Coverageinformation of which the communication control apparatus (CDIS) 30 a isnotified from the communication control apparatus (CM#B) 30 b is shownon the right side of FIG. 11. The coverage information contains thesecondary system ID, reference position, and radius of the secondarysystems N3, N4 illustrated in FIG. 6.

When such coverage information is notified, the neighbor detection unit174 of the communication control apparatus 30 a determines thepossibility of interference between secondary systems based on thedistance between reference positions and two radii for each combinationof secondary systems contained in the coverage information. If, forexample, the distance between the reference positions is smaller thanthe sum of radii, the two secondary systems have overlapping coverage.If, for example, the distance between reference positions is smallerthan one radius, it is understood that a wireless signal from thesecondary usage node 40 as the master device of one secondary system candirectly reach the secondary usage node 40 of the other secondarysystem. In both of these cases, the neighbor detection unit 174 maydetermine that the possibility of interference is present betweensecondary systems.

When some secondary system is newly added, the neighbor detection unit174 may determine only possibilities of interference between the newsecondary system and other secondary systems. In the example of FIG. 11,the neighbor detection unit 174 may additionally determine onlypossibilities of interference between the secondary system N5 and othersecondary systems.

-   -   (2) Neighboring System List

FIGS. 12 and 13 are explanatory views illustrating examples of aneighboring system list generated by the communication control apparatus30 a in the present embodiment.

The neighboring system list in FIG. 12 assumes the physical relationshipbetween secondary systems illustrated in FIG. 5. The neighboring systemlist in FIG. 12 indicates that the secondary system N1 belonging to CM#Aand the secondary system N2 belonging to CM#A are related as neighboringsystems (pair ID: A01) and the secondary system N3 belonging to CM#B andthe secondary system N4 belonging to CM#B are related as neighboringsystems (pair ID: B01). These two pairs are pairs of neighboring systemsbelonging to common CM. Such neighboring systems are called here asIntra-CM neighboring systems. On the other hand, neighboring systemsbelonging to different CM are called Inter-CM neighboring systems. NoInter-CM neighboring system is present in the neighboring system list ofFIG. 12.

In the example of FIG. 12, an attribute called “class” is attached toeach pair of neighboring systems. “Class” may be an attributerepresenting the classification of physical relationship of, forexample, the following neighboring systems:

-   -   Class C1: Master devices are wirelessly communicable    -   Class C2: Master devices are not directly communicable, but have        overlapping coverage    -   Class C3: Coverage of one secondary system is contained in        coverage of the other    -   Class C4: There is the possibility of interference due to a        short distance, though there is no overlapping coverage

Such class attributes may be used when CM adjusts the configuration ofsecondary systems to control interference. For example, for a pair ofClass C1, master devices (for example, TVBD in a TV broadcasting system)can directly communicate wirelessly. Thus, two secondary systems can beoperated without interfering with each other by assigning a frequencychannel common to two secondary systems to allow the master devices toexchange scheduling information or to form a mesh network. For a pair ofClass C2, master devices cannot directly communicate wirelessly Thus,when two secondary systems are allowed to form a mesh network, forexample, CM may be requested to feed a synchronization signal to eachmaster device. For a pair of Class C3, two secondary systems may beallowed to coexist by even signal transmission of a secondary systemhaving narrower coverage being scheduled by the master device of theother secondary system having wider coverage. Such classifications maybe decided by the neighbor detection unit 174 of the communicationcontrol apparatus 30 a using coverage information illustrated in FIG. 9or 11.

The neighboring system list in FIG. 13 assumes the physical relationshipbetween secondary systems illustrated in FIG. 6. The neighboring systemlist in FIG. 13 contains, in addition to pairs contained in theneighboring system list in FIG. 12, three pairs of neighboring systems.The first new pair is a pair of Intra-CM neighboring systems of thesecondary system N2 belonging to CM#A and the secondary system N5belonging to CM#A (pair ID: A02). The second new pair is a pair ofInter-CM neighboring systems of the secondary system N5 belonging toCM#A and the secondary system N3 belonging to CM#B (pair ID: A11). Thethird new pair is a pair of Inter-CM neighboring systems of thesecondary system N3 belonging to CM#B and the secondary system N5belonging to CM#A (pair ID: B11). The pair A11 and the pair B11 arepairs of essentially the same neighboring systems.

The neighbor detection unit 174 of the communication control apparatus30 a provides such a neighboring system list to each of thecommunication control apparatuses 30 b.

-   -   <3. Flow of Processing According to an Embodiment>

FIG. 14 is a flow chart showing an example of the flow of communicationcontrol processing for neighbor detection according to the presentembodiment.

Referring to FIG. 14, each of the secondary usage nodes 40 a, 40 b, 40 efirst collects parameters to calculate coverage of each secondary system(step S11). Similarly, each of the secondary usage nodes 40 c, 40 dcollects parameters to calculate coverage of each secondary system (stepS12).

Next, each of the secondary usage nodes 40 a, 40 b, 40 e transmits aparameter list containing collected parameters to the communicationcontrol apparatus (CM#A) 30 b (step S13). Such a parameter list isreceived by the first communication unit 110 of the communicationcontrol apparatus (CM#A) 30 b and acquired by the parameter acquisitionunit 142. Similarly, each of the secondary usage nodes 40 b, 40 ctransmits a parameter list containing collected parameters to thecommunication control apparatus (CM#B) 30 b (step S14). Such a parameterlist is received by the first communication unit 110 of thecommunication control apparatus (CM#B) 30 b and acquired by theparameter acquisition unit 142.

Next, the calculation unit 144 of the communication control apparatus(CM#A) 30 b calculates coverage of each secondary system under controlusing parameters acquired by the parameter acquisition unit 142 (stepS21). Then, the interference control unit 146 notifies the communicationcontrol apparatus 30 a of coverage information representing coverage ofeach secondary system calculated by the calculation unit 144 (step S25).

In addition, the calculation unit 144 of the communication controlapparatus (CM#B) 30 b calculates coverage of each secondary system undercontrol using parameters acquired by the parameter acquisition unit 142(step S23). Then, the interference control unit 146 notifies thecommunication control apparatus 30 a of coverage informationrepresenting coverage of each secondary system calculated by thecalculation unit 144 (step S26).

The neighbor detection unit 174 of the communication control apparatus(CDIS) 30 a determines the possibility of mutual interference for eachcombination of secondary systems using coverage information notifiedfrom the communication control apparatus 30 b to detect neighboringsystems (step S30). Then, the neighbor detection unit 174 provides aneighboring system list describing combinations of detected neighboringsystems to the communication control apparatus (CM#A) 30 b and thecommunication control apparatus (CM#B) 30 b (steps S41, S42).

Next, if the neighboring system list indicates the presence of secondarysystems that may interfere with each other, the interference controlunits 146 of the communication control apparatus (CM#A) 30 b and thecommunication control apparatus (CM#B) 30 b negotiate to controlinterference (step S50). Then, one or both of the communication controlapparatus (CM#A) 30 b and the communication control apparatus (CM#B) 30b instruct the secondary usage nodes 40 to configure or reconfigure thesystem to reflect a negotiation result in the configuration of eachsecondary system (steps S61, S62).

Incidentally, the flow of communication control processing shown in FIG.14 is only by way of example. That is, each processing step constitutingthe communication control processing may be executed in an orderdifferent from the illustrated order. In addition, a processing step notshown in FIG. 14 may additionally be executed or a part of processingsteps may be omitted.

-   -   <4. Modifications>    -   [4-1. First Modification]

In the above embodiment, an example in which CDIS determines thepossibility of interference for all combinations of secondary systems isdescribed. However, for example, CM may determine the possibility ofinterference for each combination of secondary systems under control ofCM using coverage information to detect Intra-CM neighboring systems(that is, the communication control apparatus 30 b may also include aneighbor detection unit). In such a case, CDIS determines thepossibility of interference only for combinations of secondary systemsextending over CM to detect Inter-CM neighboring systems. Accordingly,detection processing of Intra-CM neighboring systems is distributed overa plurality of CM so that the load on CDIS can further be reduced.

FIG. 15 is a flow chart showing an example of the flow of communicationcontrol processing for neighbor detection according to a firstmodification as described above. Referring to FIG. 15, each of thesecondary usage nodes 40 a, 40 b, 40 e first collects parameters tocalculate coverage of each secondary system (step S11). Similarly, eachof the secondary usage nodes 40 c, 40 d collects parameters to calculatecoverage of each secondary system (step S12).

Next, each of the secondary usage nodes 40 a, 40 b, 40 e transmits aparameter list containing collected parameters to the communicationcontrol apparatus (CM#A) 30 b (step S13). Similarly, each of thesecondary usage nodes 40 b, 40 c transmits a parameter list containingcollected parameters to the communication control apparatus (CM#B) 30 b(step S14).

Next, the communication control apparatus (CM#A) 30 b calculatescoverage of each secondary system under control using acquiredparameters (step S21) to detect Intra-CM neighboring systems fromsecondary systems belonging to CM#A (step S22). Similarly, thecommunication control apparatus (CM#B) 30 b calculates coverage of eachsecondary system under control using acquired parameters (step S23) todetect Intra-CM neighboring systems from secondary systems belonging toCM#B (step S24).

Next, the communication control apparatus (CM#A) 30 b notifies thecommunication control apparatus 30 a of coverage informationrepresenting coverage of each secondary system (step S25). Also, thecommunication control apparatus (CM#B) 30 b notifies the communicationcontrol apparatus 30 a of coverage information representing coverage ofeach secondary system (step S26).

The communication control apparatus (CDIS) 30 a uses the coverageinformation notified from these communication control apparatuses 30 bto detect Inter-CM neighboring systems from secondary systems extendingover CM#A and CM#B (step S31). Then, the communication control apparatus(CDIS) 30 a provides a neighboring system list describing combinationsof detected Inter-CM neighboring systems to the communication controlapparatus (CM#A) 30 b and the communication control apparatus (CM#B) 30b (steps S41, S42). Then, the flow of processing may be the same as thatof the communication control processing shown in FIG. 14.

-   -   [4-2. Second Modification]

Heretofore, examples in which CDIS is arranged in an apparatus that isdifferent from apparatuses in which CM is arranged have mainly beendescribed. However, CDIS may be arranged in one of apparatuses in whichCM is arranged. The technology disclosed herein is also applicable tocoexistence systems based on specifications (for example,RRS(Reconfigurable Radio Systems) of ETSI(European TelecommunicationsStandards Institute)) other than IEEE802.19. Also in such a case, inaddition to a detection node that determines the possibility ofinterference between a plurality of secondary systems to detectneighboring systems, a logical node to calculate coverage of eachsecondary system by using parameters collected from each secondarysystem is provided. Then, the detection node is notified of coverageinformation from the node that calculates coverage.

FIG. 16 is a flow chart showing an example of the flow of communicationcontrol processing for neighbor detection according to a secondmodification as described above. Referring to FIG. 16, the detectionnode that performs neighbor detection is selected in advance from amonga plurality of the communication control apparatuses 30 b (step S10).The detection node may be detected from the viewpoint of, for example,performance, capabilities, capacities of available resources, orsmallness of the number of secondary systems under control of each ofthe communication control apparatuses 30 b. In the example of FIG. 16,it is assumed that the communication control apparatus (CM#B) 30 b isselected as the detection node.

Each of the secondary usage nodes 40 a, 40 b, 40 e collects parametersto calculate coverage of each secondary system (step S11). Similarly,each of the secondary usage nodes 40 c, 40 d collects parameters tocalculate coverage of each secondary system (step S12).

Next, each of the secondary usage nodes 40 a, 40 b, 40 e transmits aparameter list containing collected parameters to the communicationcontrol apparatus (CM#A) 30 b (step S13). Similarly, each of thesecondary usage nodes 40 b, 40 c transmits a parameter list containingcollected parameters to the communication control apparatus (CM#B) 30 b(step S14).

Next, the communication control apparatus (CM#A) 30 b calculatescoverage of each secondary system under control using acquiredparameters (step S21). Then, the communication control apparatus (CM#A)30 b notifies the communication control apparatus (CM#B) 30 b ofcoverage information representing the calculated coverage of eachsecondary system (step S27). On the other hand, the communicationcontrol apparatus (CM#B) 30 b also calculates coverage of each secondarysystem under control using acquired parameters (step S23).

Next, the communication control apparatus (CMM) 30 b determines thepossibility of mutual interference for each combination of secondarysystems using coverage information notified from the communicationcontrol apparatus (CM#A) 30 b and coverage information generated by thecommunication control apparatus (CM#B) 30 b itself to detect neighboringsystems (step S30). Then, the communication control apparatus (CM#B) 30b provides a neighboring system list describing combinations of detectedneighboring systems to the communication control apparatus (CM#A) 30 b(step S41). Next, if secondary systems that may interfere with eachother are present, the communication control apparatus (CM#A) 30 b andthe communication control apparatus (CM#B) 30 b negotiate to controlinterference (step S50). Then, the flow of processing may be the same asthat of the communication control processing shown in FIG. 14.

-   -   <5. Summary>

Heretofore, an embodiment and modifications thereof have been describedin detail using FIGS. 1 to 16. According to the technology describedherein, a communication control apparatus having a function as CMcalculates coverage of each secondary system using parameters tocalculate coverage of each secondary system and a detection node thatperforms neighbor detection is notified of coverage informationrepresenting the calculated coverage of each secondary system. Thus,parameters for coverage calculation with a large amount of data are nottransmitted to the detection node and so the load of traffic in anetwork is reduced. In addition, there is no need for the detection nodeto calculate coverage of many secondary systems and so the load ofcalculation processing of the detection node is also reduced. Therefore,a plurality of secondary systems can be operated smoothly by theconcentration of load being avoided. In addition, according to the aboveembodiment, when various secondary systems are operated by a pluralityof operators, there is no need for each operator to disclose detailedparameters of systems to the operator having the detection node.Therefore, smooth coexistence of systems operated by the plurality ofoperators is enabled.

A sequence of control processing by each apparatus described herein maybe realized by using any of software, hardware, and a combination ofsoftware and hardware. A program constituting software is stored in, forexample, a storage medium provided inside or outside each apparatus.Then, each program is read into RAM (Random Access Memory) duringexecution and executed by a processor such as a CPU(Central ProcessingUnit).

The preferred embodiments of the present disclosure have been describedin detail above with reference to the accompanying drawings, whilst thetechnical scope of the present technology is not limited to the aboveexamples, of course. A person skilled in the art may find variousalterations and modifications within the scope of the appended claims,and it should be understood that they will naturally come under thetechnical scope of the present disclosure.

Additionally, the present technology may also be configured as below.

(1)

A communication control apparatus including:

-   -   a parameter acquisition unit that acquires parameters to        calculate coverage of secondary systems from a secondary usage        node operating the secondary systems on a frequency channel        allocated to a primary system;    -   a calculation unit that calculates the coverage of the secondary        systems using the parameters acquired by the parameter        acquisition unit; and    -   an interference control unit that notifies a detection node that        detects neighboring secondary systems of the secondary systems,        of coverage information representing the coverage of the        secondary systems calculated by the calculation unit.        (2)

The communication control apparatus according to (1), wherein thecoverage information is map information indicating whether each of aplurality of geographical blocks belongs to the coverage.

(3)

The communication control apparatus according to (1), wherein thecoverage information is information indicating a reference position anda radius of the coverage.

(4)

The communication control apparatus according to any one of (1) to (3),wherein the parameters indicate at least one of a position of thesecondary usage node, an antenna height, maximum transmission power, anantenna gain, and minimum reception sensitivity.

(5)

The communication control apparatus according to any one of (1) to (4),wherein when the neighboring secondary systems controlled by the othercommunication control apparatus are detected by the detection node, theinterference control unit conducts negotiations with anothercommunication control apparatus to control interference between thesecondary systems.

(6)

The communication control apparatus according to (5), wherein theinterference control unit adjusts at least one of a utilized channel, awireless access method, and maximum transmission power of the secondarysystems or the neighboring secondary systems by the negotiations.

(7)

The communication control apparatus according to (1) to (6), furtherincluding:

-   -   a neighbor detection unit that detects the neighboring secondary        systems from a plurality of the secondary systems belonging to        the apparatus,    -   wherein the detection node detects the neighboring secondary        systems belonging to the different communication control        apparatuses.        (8)

The communication control apparatus according to any one of (1) to (7),wherein the detection node is one of a plurality of the communicationcontrol apparatuses, each having a function to calculate coverage of oneor more secondary systems.

(9)

A communication control method of a control node that controlscommunication by a secondary usage node operating secondary systems on afrequency channel allocated to a primary system, the method including:

-   -   acquiring parameters to calculate coverage of the secondary        systems from the secondary usage node;    -   calculating the coverage of the secondary systems using the        acquired parameters; and    -   notifying a detection node that detects neighboring secondary        systems of the secondary systems, of coverage information        representing the calculated coverage of the secondary systems.        (10)

A communication control system, including:

-   -   a secondary usage node that operates secondary systems on a        frequency channel allocated to a primary system;    -   a control node that controls communication by the secondary        usage node; and    -   a detection node that detects neighboring secondary systems of        the secondary systems,    -   wherein the control node includes        -   a parameter acquisition unit that acquires parameters to            calculate coverage of the secondary systems from the            secondary usage node,        -   a calculation unit that calculates the coverage of the            secondary systems by using the parameters acquired by the            parameter acquisition unit, and        -   an interference control unit that notifies the detection            node of coverage information representing the coverage of            the secondary systems calculated by the calculation unit.

REFERENCE SIGNS LIST

30 a detection node

30 b communication control apparatus (control node)

40 secondary usage node

142 parameter acquisition unit

144 calculation unit

146 interference control unit

1. A communication control apparatus comprising: a parameter acquisitionunit that acquires parameters to calculate coverage of secondary systemsfrom a secondary usage node operating the secondary systems on afrequency channel allocated to a primary system; a calculation unit thatcalculates the coverage of the secondary systems using the parametersacquired by the parameter acquisition unit; and an interference controlunit that notifies a detection node that detects neighboring secondarysystems of the secondary systems, of coverage information representingthe coverage of the secondary systems calculated by the calculationunit.
 2. The communication control apparatus according to claim 1,wherein the coverage information is map information indicating whethereach of a plurality of geographical blocks belongs to the coverage. 3.The communication control apparatus according to claim 1, wherein thecoverage information is information indicating a reference position anda radius of the coverage.
 4. The communication control apparatusaccording to claim 1, wherein the parameters indicate at least one of aposition of the secondary usage node, an antenna height, maximumtransmission power, an antenna gain, and minimum reception sensitivity.5. The communication control apparatus according to claim 1, whereinwhen the neighboring secondary systems controlled by anothercommunication control apparatus are detected by the detection node, theinterference control unit conducts negotiations with the othercommunication control apparatus to control interference between thesecondary systems.
 6. The communication control apparatus according toclaim 5, wherein the interference control unit adjusts at least one of autilized channel, a wireless access method, and maximum transmissionpower of the secondary systems or the neighboring secondary systems bythe negotiations.
 7. The communication control apparatus according toclaim 1, further comprising: a neighbor detection unit that detects theneighboring secondary systems from a plurality of the secondary systemsbelonging to the apparatus, wherein the detection node detects theneighboring secondary systems belonging to the different communicationcontrol apparatuses.
 8. The communication control apparatus according toclaim 1, wherein the detection node is one of a plurality of thecommunication control apparatuses, each having a function to calculatecoverage of one or more secondary systems.
 9. A communication controlmethod of a control node that controls communication by a secondaryusage node operating secondary systems on a frequency channel allocatedto a primary system, the method comprising: acquiring parameters tocalculate coverage of the secondary systems from the secondary usagenode; calculating the coverage of the secondary systems using theacquired parameters; and notifying a detection node that detectsneighboring secondary systems of the secondary systems, of coverageinformation representing the calculated coverage of the secondarysystems.
 10. A communication control system, comprising: a secondaryusage node that operates secondary systems on a frequency channelallocated to a primary system; a control node that controlscommunication by the secondary usage node; and a detection node thatdetects neighboring secondary systems of the secondary systems, whereinthe control node includes a parameter acquisition unit that acquiresparameters to calculate coverage of the secondary systems from thesecondary usage node, a calculation unit that calculates the coverage ofthe secondary systems by using the parameters acquired by the parameteracquisition unit, and an interference control unit that notifies thedetection node of coverage information representing the coverage of thesecondary systems calculated by the calculation unit.